Rolling bearing with reinforcing member

ABSTRACT

The present invention provides a rolling bearing that prevents retainer noise and NRRO deterioration thereof by imparting strength and rigidity to a retainer so as to prevent it from being deformed by force from rolling elements and sliding friction. An annular plate is connected to a retainer by bosses. Due to the rigidity of the annular plate, the strength and rigidity of the retainer can be improved. Additionally, since the bosses are fixed to grease reservoirs arranged at an equal spacing therebetween on the circumference of the retainer, the strength and rigidity of the retainer can be equally improved over the entire circumference thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rolling bearing, and particularly, toa rolling bearing which is suitable for rotational support members ofhard disk drives (HDD), video tape recorders, office automationequipment and so forth.

2. Description of the Related Art

As shown in FIG. 4, a rolling bearing 10 consists of an inner ring 11and an outer ring 12 each having a raceway surface, and a plurality ofrolling elements 5 such as balls. Each rolling element 5 is rollablyarranged between the raceway surface of the inner ring 11 and theraceway surface of the outer ring 12. Additionally, a retainer 1rotatably holds each rolling element 5 and ring-shaped sealing members13 are arranged at each end in the axial direction.

The retainer 1, as shown in FIG. 5, is a ring body having a plurality ofball pockets 2 arranged at equal spacing therebetween, and is resinmolding which is molded in one piece. The ball pockets 2 are parts forholding the rolling elements 5 (see FIG. 4). A pair of claws 3 providedat each ball pocket 2 prevents the rolling elements 5 from falling out,and can rotatably hold the elements. Grease resevoirs 4 are arranged atequal spacing between the claws 3 adjacent ball pockets 2. Theindividual rolling elements 5 are arranged at equal spacing therebetweenby the retainer 1, thereby preventing seizure caused by the mutualcontact of the rolling elements 5.

Since the retainer 1 does not directly support a bearing load, theretainer may be made of a material having a lower strength than therolling elements 5, the inner ring 11 and the outer ring 12. However,the retainer 1 is in sliding contact with the rolling elements 5, theinner ring 11 and the outer ring 12. For instance, while the inner ring11 is rotating and the outer ring 12 is stopped during use, the rollingelements 5 rotate and revolve around the inner ring 11. The retainer 1is driven by the rolling elements 5 while the ball pockets 2 and therolling elements 5 are in sliding contact with each other, and theretainer 1 rotates around the inner ring 11 at the same speed as therevolving speed of the rolling elements 5. Thus, the retainer 1 has toresist abrasion and seizure, and is often made of a synthetic resin suchas nylon 66 by injection molding.

The retainer 1 molded from such a material can be elastically deformed.Thus, after the resin is injected into a die and solidified duringinjection molding, a product is released from the die by so-calledforced pull-out wherein the claws 3, having an undercut shape in thereleasing direction, are widened outwardly, thus simplifying thestructure of the die. Moreover, during the assembly of the rollingbearing 10, the tips of the claws 3 of the retainer 1 are pushed outwardand the rolling elements 5 are pushed into the ball pockets 2. Thus therolling elements 5 can be held rollably.

The claws 3 of the retainer 1 are made thin in consideration of thereleasing property from the die and the assembling property of therolling elements 5 described above, which has the following influence onthe characteristics of the rolling bearing 10.

A clearance is provided at a required distance between the retainer 1and the rolling elements 5 or bearing rings of the inner ring 11 and theouter ring 12. However the retainer 1 vibrates despite the clearancebeing filled and supplied with grease. In addition, noise, the so-calledretainer noise, and vibration are generated. Specific causes for theretainer noise are such as:

(1) collision between the retainer 1 and the rolling elements 5 orbearing rings of the inner ring 11 and the outer ring 12,

(2) self-excited vibration due to sliding friction between the rollingelements 5 and the retainer 1,

(3) collision between the retainer 1 and the rolling elements 5 due togrease resistance,

(4) vibration due to waviness of the raceway rings surface of the innerring 11 and the outer ring 12, and rolling contact surfaces of therolling elements 5, and

(5) vibration frequency of the shaft portion is close to the resonancefrequency of the retainer 1.

In addition, run-out is found in revolution frequencies of the rollingelements 5 due to mutual differences in diameter of the rolling elements5 and disproportionate arrangement of the rolling elements 5 in acircumferential direction. Accordingly, the vibration fluctuates duringthe rotation of the rolling bearing 10, and non-repetitive run-out(NRRO) intensifies. Thus, infinitesimal displacement occurs, whichresults in uneven rotation of HDD and so forth and to deterioration ofperformance by characteristics such as NRRO. Particularly, when therolling bearing is used at high rotation (12,000 to 15,000 rpm), a forcefrom the rolling elements 5 works on a thin part of the retainer 1, thusdeforming the retainer. In addition, the claws 3 are expanded,increasing the moving area of the rolling elements 5 and therebyintensifying collision noise. The rolling elements 5 are also greatlyshifted, which results in the disproportionate arrangement of therolling elements in the circumferential direction and the deteriorationof the NRRO.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to impart strengthand rigidity to a retainer to prevent if from deformation by forcecoming from the rolling elements and sliding friction withoutdeteriorating its releasing property from a die and assembling propertyof the rolling elements, thus preventing retainer noise and NRROdeterioration of a rolling bearing.

In order to solve the above problems, a rolling bearing according to afirst aspect of the invention comprises a resinous retainer having apair of claws at each of a plurality of ball pockets arranged at equalspacing therebetween so as to prevent rolling elements from falling out,and a separate reinforcing member fixed to the retainer. In other words,since the separate reinforcing member is fixed to the retainer in thepresent invention, strength and rigidity of the retainer is improved.

Moreover, the reinforcing member may have an annular plate and aplurality of bosses fixed to grease resevoirs of the retainer. Accordingto the present invention, the bosses connect the annular plate to theretainer, and the strength and rigidity of the retainer can be improveddue to the rigidity of the annular plate. The grease reservoirs arepreferably arranged at an equal spacing therebetween on thecircumference of the retainer, so that the strength and rigidity of theretainer can be equally improved over the entire circumference byconnecting the bosses to the retainer at the grease reservoirs.

The annular plate may have openings so as not to touch the rollingelements. In this configuration, the annular plate and the rollingelements are by no means in contact with each other even when theretainer is set closer to the annular plate. Thus, a space for settingthe reinforcing member can be reduced as much as possible, and thebosses can be shortened as much as possible, thereby preferablyimproving the rigidity and strength of the retainer.

Furthermore, the grease resevoirs of the retainer can be provided withholes to which the bosses of the reinforcing member are press-fit. Inthis configuration, the reinforcing member can be fixed to the retainermore simply.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a rolling element and a retainer, and asectional view of a reinforcing member of a rolling bearing according toan embodiment of the present invention;

FIG. 2 is a perspective view of the retainer shown in FIG. 1;

FIG. 3 is a perspective view of the reinforcing member shown in FIG. 1;

FIG. 4 is a perspective view in section, showing a conventional rollingbearing; and

FIG. 5 is a perspective view of a retainer of the rolling bearing shownin FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be explained alongwith the attached drawings. The same reference numerals are used for thesame or equivalent parts as those of a conventional art, and thedetailed explanation thereof is omitted herein.

FIG. 1 shows a rolling element 5, a retainer 6 and a separatereinforcing member 8 which is fixed to the retainer 6, of a rollingbearing according to an embodiment of the invention seen from the side(cross section for the reinforcing member 8). FIG. 2 is a partial viewof the retainer 6. FIG. 3 is a overall view of the reinforcing member 8.

The retainer 6 has nearly the same configuration as the conventionalretainer 1 (see FIG. 5), but is different from the conventional retainer1 since grease reservoirs 4 are provided with holes 7. The depth of theholes 7 is 30% to 70% of a thickness of the grease reservoirs 4 on theretainer 6. The rest is the same as that of the conventional retainer 1in that the retainer 6 is made of a synthetic resin such as nylon 66 byinjection molding.

The reinforcing member 8 is provided with a plurality of bosses 8 b, andopenings 8 c to keep the reinforcing member 8 away from the rollingelements 5, at an annular plate 8 a. The outside diameter of the annularplate 8 a is 80% to 120% of the outside diameter of the retainer 6. Thethickness of the annular plate 8 a is 20% to 80% of the thickness of thegrease reservoirs 4 on the retainer 6. Moreover, the openings 8 c havespherical inner surfaces corresponding to the rolling elements 5, andthe diameter from a center point is 100% to 120% of the diameter of therolling elements 5. Furthermore, the length of the bosses 8 b is 20% to60% of the width of the retainer 6 (difference between an insidediameter and an outside diameter). It is preferable that the reinforcingmember 8 is made of nylon 66 like the retainer 6, or a synthetic resinsuch as a resin in which glass fiber is mixed into nylon 66 up to 30%,polyacetal, liquid crystal polymer or the like, and is manufactured byinjection molding.

The reinforcing member 8 is fixed to the retainer 6 after the tips ofthe claws 3 of the retainer 6 are pushed out and the rolling elements 5are pushed into ball pockets 2. The bosses 8 b are welded to the holes 7provided at the grease reservoirs 4 on the retainer 6, by press-fit orultrasonic, so that the reinforcing member 8 is fixed to the retainer 6more simply. The bosses 8 b protrude from the surface of the retainer 6by only 50% to 100% of the diameter of the rolling members 5, in apress-fit condition to the holes 7 of the retainer 6. Additionally,although not shown in the drawings, the bosses 8 b may be so-calledstepped bosses, so that the reinforcing member 8 can be positioned tothe retainer 6 with greater accuracy and certainty.

Moreover, each rolling element 5 held rollably by the retainer 6 ispositioned with a constant gap in relation to the openings 8 c of theannular plate 8 a while the reinforcing member 8 is fixed to theretainer 6. The rolling elements 5 are by no means directly in contactwith the annular plate 8 a.

FIG. 3 shows the reinforcing member 8 having six bosses 8 b and sixopenings 8 c. This reinforcing member 8 is used for the retainer 6having six ball pockets 2 and six grease reservoirs 4. Accordingly, itis obvious that the number of bosses 8 b and openings 8 c of thereinforcing member 8 is not limited to that shown in the drawings.Moreover, since an inner ring, an outer ring and ring-form seal membersof the rolling bearing according to the preferred embodiment of thepresent invention have the same configurations as those of theconventional rolling bearing 10 (see FIG. 4), the detailed explanationthereof is omitted.

The above-mentioned embodiment of the present invention can exert thefollowing effects. First, the bosses 8 b connect the annular plate 8 ato the retainer 6, so that the strength and rigidity of the retainer 6can be improved due to the rigidity of the annular plate 8 a.Additionally, the bosses 8 b are fixed to the grease reservoirs 4arranged at equal spacing therebetween on the circumference of theretainer 6, so that the strength and rigidity of the retainer 6 can beequally improved over the entire circumference.

Moreover, since the openings 8 c are formed on the annular plate 8 a,each rolling element 5 held rollably by the retainer 6 is by no meansdirectly in contact with the annular plate 8 a even when the retainer 6is set closer to the annular plate 8 a. Thus, a space for setting thereinforcing member 8 can be reduced as much as possible, so that theretainer 6 may be simply substituted for the conventional retainer 1(FIG. 4 and FIG. 5) for use. Additionally, the bosses 8 b can beshortened as much as possible in order to improve rigidity and strengthwhen the reinforcing member 8 is fixed to the retainer 6.

Furthermore, the bosses 8 b are press-fit and then welded to the holes 7provided at the grease reservoirs 4 on the retainer 6. Accordingly, thereinforcing member 8 can be fixed to the retainer 6 more simply, and theincrease in manufacturing costs can be prevented as much as possible.When the reinforcing member 8 is made of the same material as theretainer 6, the welding operation can be carried out much easier.

Being configured as mentioned above, the present invention has thefollowing effects. First, according to the first aspect of the presentinvention, strength and rigidity can be imparted to the retainer so asto prevent it from being deformed by force from the rolling elements andsliding friction, without reducing its releasing property from a die andassembling property of the rolling elements. Accordingly, retainer noiseand NRRO deterioration of the rolling bearing can be prevented.

Moreover, the strength and rigidity of the retainer can be improved dueto the rigidity of an annular plate. Additionally, the strength andrigidity of the retainer can be equally improved over the entirecircumference thereof.

The rigidity and strength of the retainer can be improved, so that theretainer noise and NRRO deterioration of the rolling bearing can beprevented.

Furthermore, a reinforcing member can be fixed to the retainer moresimply, thereby preventing increases in manufacturing costs.

What is claimed is:
 1. A rolling bearing comprising: a resinous retainerhaving a pair of claws at each of a plurality of ball pockets arrangedwith a equal spacing therebetween so as to prevent rolling elements fromfalling out; and a separate reinforcing member fixed to the retainer. 2.A rolling bearing according to claim 1, wherein the reinforcing membercomprises an annular plate, and a plurality of bosses which are fixed togrease reservoirs of the retainer.
 3. A rolling bearing according toclaim 2, wherein the annular plate is provided with openings so as notto contact the rolling elements.
 4. A rolling bearing according to claim3, wherein the grease reservoirs of the retainer are provided with holesto which the bosses of the reinforcing member are press-fit.
 5. Arolling bearing according to claim 2, wherein the grease reservoirs ofthe retainer are provided with holes to which the bosses of thereinforcing member are press-fit.